This invention relates generally to apparatus and methods for removing underground cables, and more particularly to such apparatus and methods which pulls the cable by means of a rotating wheel or sheave.
Often it is desired to remove telephone cable and the like which has been placed underground for long periods of time and needs to be replaced. Typically, the cable is actually located in a clay, ceramic or plastic duct. However, over the years the cable becomes fixed in sections of duct due to dirt accumulation and shifting of the sections of the duct so that it becomes extremely difficult to remove without digging up the entire length of cable.
Such cable is usually constructed of a core comprising hundreds of twisted pairs of insulated wire conductors surrounded by a sheath of plastic or lead. It is essential that the entire cable, both sheathing and the bundled core of conductors, be removed in order that the duct can be reused to lay a new cable. The lead sheathing used in much of the cable being removed at this time is in such condition and quality that generally it tends to separate or disintegrate when attempts are made to remove it with conventional equipment such as a winching arrangement that grips the end of the cable and pulls out a section which is then cut off and the next section is removed. Thus, removal progresses intermittently. Similar problems exist with the plastic sheathed underground cable.
Several problems result from such intermittent progress. One problem is that each pull must overcome static friction. Another problem is that the stresses created by such intermittent motion allows the withdrawal of only a relatively short length of cable, and so a new hole must be dug and the equipment remobilized to a new work position to continue the removal of the cable.